2,896 research outputs found
Quantum correlations and thermodynamic performances of two-qubit engines with local and collective baths
We investigate heat engines whose working substance is made of two coupled
qubits performing a generalised Otto cycle by varying their applied magnetic
field or their interaction strength during the compression and expansion
strokes. During the heating and cooling strokes, the two qubits are coupled to
local and common environments that are not necessarily at equilibrium. We find
instances of quantum engines coupled to non equilibrium common environments
exhibiting non-trivial connections to quantum correlations as witnessed by a
monotonic dependence of the work produced on quantum discord and entanglement.Comment: Close to published versio
Real-time Dynamics in U(1) Lattice Gauge Theories with Tensor Networks
Tensor network algorithms provide a suitable route for tackling real-time
dependent problems in lattice gauge theories, enabling the investigation of
out-of-equilibrium dynamics. We analyze a U(1) lattice gauge theory in (1+1)
dimensions in the presence of dynamical matter for different mass and electric
field couplings, a theory akin to quantum-electrodynamics in one-dimension,
which displays string-breaking: the confining string between charges can
spontaneously break during quench experiments, giving rise to charge-anticharge
pairs according to the Schwinger mechanism. We study the real-time spreading of
excitations in the system by means of electric field and particle fluctuations:
we determine a dynamical state diagram for string breaking and quantitatively
evaluate the time-scales for mass production. We also show that the time
evolution of the quantum correlations can be detected via bipartite von Neumann
entropies, thus demonstrating that the Schwinger mechanism is tightly linked to
entanglement spreading. To present the variety of possible applications of this
simulation platform, we show how one could follow the real-time scattering
processes between mesons and the creation of entanglement during scattering
processes. Finally, we test the quality of quantum simulations of these
dynamics, quantifying the role of possible imperfections in cold atoms, trapped
ions, and superconducting circuit systems. Our results demonstrate how
entanglement properties can be used to deepen our understanding of basic
phenomena in the real-time dynamics of gauge theories such as string breaking
and collisions.Comment: 15 pages, 25 figures. Published versio
A generalized phase space approach for solving quantum spin dynamics
Numerical techniques to efficiently model out-of-equilibrium dynamics in
interacting quantum many-body systems are key for advancing our capability to
harness and understand complex quantum matter. Here we propose a new numerical
approach which we refer to as GDTWA. It is based on a discrete semi-classical
phase-space sampling and allows to investigate quantum dynamics in lattice spin
systems with arbitrary . We show that the GDTWA can accurately
simulate dynamics of large ensembles in arbitrary dimensions. We apply it for
spin-models with dipolar long-range interactions, a scenario arising in
recent experiments with magnetic atoms. We show that the method can capture
beyond mean-field effects, not only at short times, but it also correctly
reproduces long time quantum-thermalization dynamics. We benchmark the method
with exact diagonalization in small systems, with perturbation theory for short
times, and with analytical predictions made for closed system which feature
quantum-thermalization at long times. By computing the Renyi entropy, currently
an experimentally accessible quantifier of entanglement, we reveal that large
systems can feature larger entanglement than corresponding systems.
Our analyses demonstrate that the GDTWA can be a powerful tool for modeling
complex spin dynamics in regimes where other state-of-the art numerical methods
fail
The role of quantum information in thermodynamics --- a topical review
This topical review article gives an overview of the interplay between
quantum information theory and thermodynamics of quantum systems. We focus on
several trending topics including the foundations of statistical mechanics,
resource theories, entanglement in thermodynamic settings, fluctuation theorems
and thermal machines. This is not a comprehensive review of the diverse field
of quantum thermodynamics; rather, it is a convenient entry point for the
thermo-curious information theorist. Furthermore this review should facilitate
the unification and understanding of different interdisciplinary approaches
emerging in research groups around the world.Comment: published version. 34 pages, 6 figure
Lattice gauge theories simulations in the quantum information era
The many-body problem is ubiquitous in the theoretical description of
physical phenomena, ranging from the behavior of elementary particles to the
physics of electrons in solids. Most of our understanding of many-body systems
comes from analyzing the symmetry properties of Hamiltonian and states: the
most striking example are gauge theories such as quantum electrodynamics, where
a local symmetry strongly constrains the microscopic dynamics. The physics of
such gauge theories is relevant for the understanding of a diverse set of
systems, including frustrated quantum magnets and the collective dynamics of
elementary particles within the standard model. In the last few years, several
approaches have been put forward to tackle the complex dynamics of gauge
theories using quantum information concepts. In particular, quantum simulation
platforms have been put forward for the realization of synthetic gauge
theories, and novel classical simulation algorithms based on quantum
information concepts have been formulated. In this review we present an
introduction to these approaches, illustrating the basics concepts and
highlighting the connections between apparently very different fields, and
report the recent developments in this new thriving field of research.Comment: Pedagogical review article. Originally submitted to Contemporary
Physics, the final version will appear soon on the on-line version of the
journal. 34 page
Kosterlitz-Thouless scaling at many-body localization phase transitions
We propose a scaling theory for the many-body localization (MBL) phase
transition in one dimension, building on the idea that it proceeds via a
'quantum avalanche'. We argue that the critical properties can be captured at a
coarse-grained level by a Kosterlitz-Thouless (KT) renormalization group (RG)
flow. On phenomenological grounds, we identify the scaling variables as the
density of thermal regions and the lengthscale that controls the decay of
typical matrix elements. Within this KT picture, the MBL phase is a line of
fixed points that terminates at the delocalization transition. We discuss two
possible scenarios distinguished by the distribution of rare, fractal thermal
inclusions within the MBL phase. In the first scenario, these regions have a
stretched exponential distribution in the MBL phase. In the second scenario,
the near-critical MBL phase hosts rare thermal regions that are power-law
distributed in size. This points to the existence of a second transition within
the MBL phase, at which these power-laws change to the stretched exponential
form expected at strong disorder. We numerically simulate two different
phenomenological RGs previously proposed to describe the MBL transition. Both
RGs display a universal power-law length distribution of thermal regions at the
transition with a critical exponent , and continuously varying
exponents in the MBL phase consistent with the KT picture.Comment: 17 pages, 10 figures; v3. minor changes, as published; v2. added
section and appendix with new numerical simulations, expanded discussio
- …